Amorphous metal rivet systems

ABSTRACT

A family of rivets including both blind and bucked-type rivets made at least partially from an amorphous metal alloy. A blind rivet includes a head portion and a tail portion. At least one of the head portion and the tail portion is configured to elastically deform to secure a first member in position relative to a second member. The head portion and the tail portion may include one or more deformable legs having an interface feature configured to engage with one of the first member and the second member. A bucked-type rivet assembly includes a formable member and an anvil. The anvil is configured to thermoplastically deform the formable member proximate to the second member by passing current through an electrical circuit that includes at least one of the formable member and anvil.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 62/735,225, filed Sep. 24, 2018, the entire disclosureof which is hereby incorporated by reference herein.

BACKGROUND

The present disclosure relates generally to the field of permanentmechanical fasteners. More specifically, the present disclosure relatesto rivets, which are traditionally used to fasten together two or moremetal plates. These include blind rivets applied from one side of astack of workpieces being joined as well as standard rivets whoseinstallation require access to both sides of the stack of workpieces.

SUMMARY

One embodiment relates to a blind rivet made at least partially from anamorphous metal alloy. The blind rivet includes a head portion and atail portion. The tail portion includes a first leg and a second leg.The tail portion further includes a tail interface disposed on an end ofeach of the first leg and the second leg. The head portion is configuredto engage with a first member. The tail interface for each of the firstleg and the second leg is configured to engage with a second member. Atleast one of the first leg and the second leg is configured toelastically deform to secure the first member in position relative tothe second member.

In any of the above embodiments, the head portion may be configured todeform elastically when securing the first member to the second member.In any of the above embodiments, the blind rivet may include a sleevedisposed proximate to the tail interface to facilitate installation ofthe blind rivet.

In some embodiments, the blind rivet may include a third leg and afourth leg, both disposed on the head portion. The blind rivet mayfurther include a pulling member disposed proximate to the third leg andthe fourth leg, the pulling member configured to facilitate installationof the blind rivet.

Another embodiment relates to a bucked-type rivet assembly. Thebucked-type rivet assembly includes a formable member made from anamorphous metal alloy. An anvil configured to facilitate installation ofthe formable member is at least partially disposed in a channel throughthe formable member. The anvil includes an interface shaft and an anvilhead disposed on a first end of the interface shaft. The formable memberis configured to secure a first member in position relative to a secondmember. The anvil head is configured to plastically deform the formablemember proximate to the second member. The anvil head is furtherconfigured to separate from the interface shaft upon application of apredetermined tensile force to the interface shaft.

In some embodiments, the bucked-type rivet assembly may form anelectrical circuit that includes at least one of the anvil and theformable member.

In some embodiments, the formable member may be heated by exciting theanvil ultrasonically or spinning the anvil rapidly across one or moresurfaces of the formable member.

Another embodiment relates to a method of installation for a bucked-typerivet. The method includes inserting a formable member through a firstaperture in a first member and a second aperture in a second member. Themethod also includes inserting an anvil into a channel in the formablemember. The anvil includes an interface shaft and an anvil head disposedon a first end of the interface shaft. The anvil additionally includesan insulating layer disposed on an outer surface of the interface shaft.The method further includes passing current through an electricalcircuit including the interface shaft, the anvil head, and the formablemember. The method additionally includes pulling on the interface shaftto deform a portion of the formable member. The method also includesbreaking the interface shaft.

This summary is illustrative only and is not intended to be in any waylimiting. Other aspects, inventive features, and advantages of thedevices and/or processes described herein, as defined solely by theclaims, will become apparent in the detailed description set forthherein, taken in conjunction with the accompanying figures, wherein likereference numerals refer to like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a blind rivet at a cross-section through aplane parallel to an axis of the blind rivet, according to anillustrative embodiment.

FIG. 2A is a side view of a blind rivet with a deformable head portion,shown at a cross-section through a plane parallel to an axis of therivet, according to an illustrative embodiment.

FIG. 2B is a side view of the blind rivet of FIG. 2A securing together astack of workpieces, according to an illustrative embodiment.

FIG. 3A is a side view of a blind rivet that includes deformable legs onboth a head portion and a tail portion of the blind rivet, shown at across-section through a plane parallel to an axis of the blind rivet,according to an illustrative embodiment.

FIG. 3B is a side view of the blind rivet of FIG. 3A securing together astack of workpieces, according to an illustrative embodiment.

FIG. 4 is a side view of a blind rivet that includes a second set ofbarbs on a head portion of the blind rivet, shown at a cross-sectionthrough a plane parallel to an axis of the blind rivet, according to anillustrative embodiment.

FIG. 5 is a side view of a two-piece blind rivet, at a cross-sectionthrough a plane parallel to an axis of the blind rivet, according to anillustrative embodiment.

FIG. 6 is a bucked-type rivet and forming piece, at a cross-sectionthrough a plane parallel to an axis of the bucked-type rivet, accordingto an illustrative embodiment.

FIG. 7A is a side perspective view of the bucked-type rivet of FIG. 6.

FIG. 7B is a side view of the forming piece of FIG. 6.

FIG. 8 is a side perspective view of an applicator device for abucked-type rivet, according to an illustrative embodiment.

FIG. 9 is a flow chart outlining a method according to an exemplaryembodiment.

FIG. 10 is a side view of a bucked-type rivet securing together a stackof workpieces, shown at a cross-section through a plane parallel to thebucked-type rivet, according to an illustrative embodiment.

FIG. 11 is a side view of the bucked-type rivet of FIG. 10 afterseparating the forming piece, according to an illustrative embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentdisclosure is not limited to the details or methodology set forth in thedescription or illustrated in the figures. It should also be understoodthat the terminology used herein is for the purpose of description onlyand should not be regarded as limiting.

Traditionally, rivets are made from materials that are harder than thosebeing joined. However, the growing use of high-strength alloys has madefinding a suitable rivet material problematic. Many of the failure modestypically associated with riveted joints, including excessive tensilestresses, shear stresses, and pull out of the rivet from the joint, maybe addressed with improved material properties of the rivet and alsobetter contact force mechanics between the rivet and workpieces beingjoined.

Referring generally to the figures, a family of rivets is provided. Therivets are made at least partially from an amorphous metal alloy such asbulk metallic glass (BMG). Two types of rivets are provided, includingelastic brad-type rivets (e.g., a blind rivet inserted from one side ofa stack of workpieces being joined) and standard or bucked-type rivets,which are secured in position by plastically deforming at least one endof the rivet. The design of the elastic brad-type rivets leverages theunique properties of BMG, a material that is able to accommodate largeamounts of elastic deformation, to secure together two or moreworkpieces (e.g., metal plates). The elastic brad-type rivets may bemechanically compressed and inserted through a joining hole in theworkpieces. A set of barb-like features on a tail end of each of thebrad-type rivets deploys near an outer edge of the joining hole, whichlocks the rivet in place. Elastic deformation of the tail end of eachbrad-type rivet results in a tensile force that locks the workpiecestogether.

Each rivet in a family of bucked-type rivets disclosed herein is securedin place by thermoplastically deforming a portion of the rivet, eitheron one or both sides of a stack of workpieces. Accordingly, installationprocedures generally require access to both sides of the stack ofworkpieces being joined. A riveting tool or other applicator device isused to facilitate installation of each of the bucked-type rivets. Forexample, the riveting tool may generate an electrical current throughthe BMG to rapidly heat the BMG while simultaneously applying a force orpressure to thermoplastically deform a portion of the rivet. Thisparticular bucked-type rivet design lends itself to use with a gas orliquid delivery system to quickly cool the rivet after the formingprocess is complete.

The riveting tool may interface with a sacrificial piece of material oranvil through which the force is transmitted to the bucked-type rivet.As an alternative to heating the material using an electrical current,the riveting tool may heat the material by spinning the anvil rapidlyacross the surface of the rivet, applying ultrasonic energy to theanvil, or otherwise mechanically exciting the anvil. The details of thegeneral depictions provided above will be more fully explained byreference to FIGS. 1-10.

Referring now to FIG. 1, a blind rivet, shown as brad rivet 100, isprovided. The brad rivet 100 is a permanent mechanical fastenerconfigured to secure two or more workpieces in position relative to oneanother. There are a wide variety of potential applications for the bradrivet 100. In one embodiment, the brad rivet 100 is used to secure aseries of metal plates together for the hull of a ship. In otherembodiments, the brad rivet 100 is used to secure thin aluminum platestogether in the construction of an aircraft cockpit and fuselage. Thebrad rivet 100 provides a viable alternative to welding and bolting,particularly for projects where the final weight of the bondedworkpieces is a key consideration.

In an illustrative embodiment, the brad rivet 100 is configured tosecure two workpieces (e.g., steel or aluminum plates, etc.) together ina stack, shown as stack 110. In alternative embodiments, the number ofworkpieces being joined may be greater. The stack 110 includes a firstmember, shown as first metal plate 112 and a second member, shown assecond metal plate 114, that are arranged in direct contact with oneanother. The thickness of each metal plate may vary depending onstructural requirements. In the embodiment of FIG. 1, the metal plates112, 114 are approximately equal in thickness. As shown in FIG. 1, thebrad rivet 100 is inserted through an aperture 116 that extends througheach of the first metal plate 112 and the second metal plate 114. In theembodiment of FIG. 1, the aperture 116 includes a first aperture 118disposed in the first metal plate 112 and a second aperture 120 disposedin the second metal plate 114. Both the first aperture 118 and thesecond aperture 120 are circular holes. The first aperture 118 has adiameter that is greater than the second aperture 120 to accommodate asleeve 126 for the brad rivet 100. In other embodiments, the size andshape of each of the first aperture 118 and the second aperture 120 maybe different.

A variety of suitable amorphous metal alloys may be used for the bradrivet 100. In particular, amorphous metal alloys including BMG alloysand/or crystalline metals characterized by a very large elastic limitand a high tensile strength may be used. Advantageously, BMG alloys witha large elastic limit (the upper range of strain an elastic material canhandle before failure) enable the brad rivet 100 to be compressed intosmaller apertures and deploy into a larger state for maximumgripping/clamping/holding power. A suitable BMG alloy may have anelastic limit of about 2% strain or greater, which is about four timeshigher than typical crystalline metals. Among various alternatives, theamorphous metal alloy may comprise a zirconium-based BMG alloy or anickel-based BMG alloy, both of which have a low manufacturing cost.Alternatively, or in addition, it may be desired to have a material withimproved fatigue life to avoid failure of the brad rivet 100 due tovibration or stress corrosion in atmospheric or more corrosiveenvironments such as seawater.

In the illustrative embodiment shown in FIG. 1, the brad rivet 100includes a head portion, shown as head 140, and a tail portion, shown astail 160, disposed at an opposite end of the brad rivet 100. The bradrivet 100 further includes a shaft, shown as cylindrical extension 180,disposed between the head 140 and the tail 160. As shown in FIG. 1, thehead 140 of the brad rivet 100 is formed in a domed shape having aplanar lower surface, shown at flat lower surface 142, that is arrangedin contact with an outer surface 124 of the first metal plate 112. Inother embodiments, the shape of the head 140 may be different. Forexample, the head 140 could be in the shape of a rectangle with uniformcross-section. Alternatively, the head 140 could be circular withuniform cross-section or any other shape that suitably interfaces withthe first metal plate 112 and prevents the brad rivet 100 from passingthrough the first aperture 118.

As shown in FIG. 1, the tail 160 of the brad rivet 100 includes twolegs, a first leg 162 and a second leg 164, which are curved away fromone another (e.g., peeled back toward the head 140 of the brad rivet100). In the embodiment of FIG. 1, the first and second legs 162, 164are in a shape formed by splitting the cylindrical extension 180 along aplane oriented parallel to a longitudinal axis 102 of the brad rivet100, resulting in legs 162, 164 that each have a substantiallysemi-circular cross-sectional shape. Other embodiments may include morelegs, each having a similar cross-sectional area. Alternatively one ormore legs may be larger or smaller than the other legs.

According to an illustrative embodiment, each of the first leg 162 andthe second leg 164 include a tail interface, shown as barb 166,configured to engage with the second metal plate 114. Once installed,the barb 166 prevents the brad rivet 100 from being removed from eitherthe first or second apertures 118, 120. The barb 166 is a smallprojection that extends outward and away from the longitudinal axis 102of the brad rivet 100. For example, the barb may be a sharp point, aridge configured to dig into a material, a hook shaped extensionconfigured to grab or lock onto an outer edge of a material, or anycombination thereof. During installation, the first and second legs 162,164 are held proximate to one another in compression by at least one ofthe first aperture 118 and the second aperture 120. Once the brad rivet100 is inserted past a predetermined point, the first leg 162 and thesecond leg 164 deploy (e.g., separate away from one another), latchingonto the second metal plate 114 at a location that is proximate to anouter edge 122 of the second aperture 120 (e.g., at a location that isjust beyond the outer edge 122 or at another anchoring point along aninterior surface of the second aperture 120). In the embodiment shown inFIG. 1, a separation distance 168 between the first leg 162 and thesecond leg 164 increases as the head 140 of the brad rivet 100 movescloser to the outer surface 124 of the first metal plate 112.

The brad rivet 100 takes advantage of the high elastic limit of BMG in ageometry that can be compressed, inserted through the joining aperture,and secured in position by nature of the resulting forces on the bradrivet 100. The brad rivet is shown in an installed position in FIG. 1.In the embodiment of FIG. 1, elastic tensile forces generated in therivet are configured to secure the first member in position relative tothe second member. The separation of the first and second legs 162, 164beyond the outer surface of the second metal plate 114, generates atensile force on the brad rivet 100. This tensile force acts to preventthe first metal plate 112 and the second metal plate 114 from separatingfrom one another and from separating from the head 140 of the brad rivet100. Although the compressive force acting on the first and second legs162, 164 is reduced when the brad rivet 100 is fully installed, thereremains an amount of compression that maintains the legs 162, 164 insolid contact with the second metal plate 114, even when stresses orvibrations are applied to the joined workpieces.

Advantageously, installation of the brad rivet 100 requires access toonly one side of the stack 110. In an illustrative embodiment, the bradrivet 100 is inserted into the first aperture 118 by compressing each ofthe first leg 162 and the second leg 164 toward one another (e.g.,toward the longitudinal axis 102 of the brad rivet 100), therebyreducing the separation distance 168 between the first and second legs162, 164 such that an outer diameter of the tail 160 is less than aninner diameter of the second aperture 120. There are a variety of toolsthat may be used to compress the first and second legs 162, 164. In theembodiment of FIGS. 1 and 2A, a compressive force is applied by placinga sleeve 126, 226 around the tail 160, 260 of the brad rivet 100. Thesleeve 126, 226 is a device configured to position the legs 162, 164,262, 264 before installation of brad rivet 100, 200. For example, thesleeve may be any one of a hollow cylinder, a removable C-clip or clasp,or a combination thereof. The sleeve 126, 226 in FIGS. 1 and 2A takesthe form of a short hollow cylinder. As shown in FIG. 2A, beforeinserting the brad rivet 200 into the first aperture 118, the sleeve 226is centered on the barbs 266 such that the barbs 266 contact an innersurface 228 of the sleeve 226. Alternatively, the sleeve 226 may bedisposed on a portion of the tail 260 just above the barbs 266, in whichcase the barbed portion of the tail 260 may be used to help center thebrad rivet 200 with respect to at least one of the first aperture 118and the second aperture 120 prior to installation.

As shown in FIG. 1, the sleeve 126 of the brad rivet 100 is configuredto facilitate installation of the brad rivet 100. In the embodiment ofFIG. 1, a diameter of the first aperture 118, shown as first aperturediameter 130, is greater than a diameter of the second aperture 120,shown as second aperture diameter 132. The sleeve 126 is configured toengage with the first aperture 118. Additionally, the sleeve 126 alignsthe brad rivet 100 with the center of the first aperture 118. In anillustrative embodiment, a height of the sleeve 126 may be less than orequal to a thickness of the first metal plate 112 so that the sleeve 126may be fully inserted into the first aperture 118. In other embodiments,the height of the sleeve 126 is greater than the thickness of the firstmetal plate 112 and is engageable with both the first aperture 118 and aslot 134 in the second metal plate 114 (thereby aligning the brad rivet100 with the center of the second aperture 120). In yet otherembodiments, the brad rivet 100 is installed without a sleeve 126. Forexample, the first aperture diameter 130 may be sized to receive acurved edge 170 of the barbs 166, the curved edge 170 configured toguide each of the first leg 162 and the second leg 164 together towardthe longitudinal axis 102 of the brad rivet 100 as the tail 160 entersthe first aperture 118.

In an illustrative embodiment, a driving tool (e.g., a hammer or otherdriving tool configured to force the tail 160 of the brad rivet 100 intothe second aperture 120) is used to secure the brad rivet 100 inposition relative to the metal plates 112, 114. A method of installationfor the brad rivet 100 includes inserting the sleeve 126 into the firstaperture 118 and using the driving tool to force the tail 160 of thebrad rivet 100 out of the sleeve 126 and into the second aperture 120(e.g., by repeatedly contacting the head 140 of the brad rivet 100 withthe driving tool). During installation, the sleeve 126 remains fixed inposition relative to the metal plates 112, 114. Installation of the bradrivet 100 is complete once the flat lower surface 142 of the head 140contacts the first metal plate 112.

In an illustrative embodiment (not shown), at least one of the firstaperture diameter 130 and the second aperture diameter 132 may be largerthan an outer diameter of the cylindrical extension 180 between the head140 and the tail 160 of the brad rivet 100. This additional space (e.g.,a small annular gap between the brad rivet 100 and the workpieces beingjoined) is at least partially accommodated by the large amount ofelastic displacement of the first and second legs 162, 164 of the bradrivet 100.

FIGS. 2A and 2B show an illustrative embodiment of a brad rivet 200including a head portion, shown as head 240, that is configured todeform elastically. As shown in FIG. 2A, the head 240 of the brad rivet200 is formed in a domed shape having a planar lower surface, shown asflat lower surface 242. The brad rivet 200 includes a pair of legs, afirst leg 262, and a second leg 264, disposed on a tail portion, shownas tail 260, of the brad rivet 200. Prior to installation, as shown inFIG. 2A, each of the first leg 262 and the second leg 264 are compressedtogether toward a longitudinal axis for the brad rivet 200 by a sleeve226.

The methods used for the installation of the brad rivet 100 of FIG. 1may also be used for the installation of the brad rivet 200 of FIG. 2A.FIG. 2B shows the same brad rivet 200 as FIG. 2A, after joining thefirst metal plate 112 and the second metal plate 114. As shown in FIG.2B, the first leg 262 and second leg 264 are deployed (e.g., separatedfrom one another) beyond an outer edge 122 of the second aperture 120.The first leg 262 and the second leg 264 contact the outer edge 122 ofthe second aperture 120, preventing the brad rivet 200 from being pulledback through the second aperture 120.

In the embodiments of FIGS. 2A and 2B, a portion of the elastic tensileforce generated within the brad rivet 200 results from deformation ofthe head 240. During installation of the brad rivet 200, as shown inFIG. 2B, a portion of the head 240 deforms elastically, resulting inrecessed portion, shown as dimple 268, in the head 240. As the head 240returns to its original geometry (shown in FIG. 2A), the metal plates112, 114 are brought together by the elastic tensile forces generated inthe brad rivet 200. In other words, the combined deformation of the head240 and the first and second legs 162, 164 generates an elastic tensileforce within the brad rivet 200 that compresses the metal plates 112,114 together between the head 240 and the tail 260.

Yet another illustrative embodiment of a brad rivet 300 is shown inFIGS. 3A and 3B. As shown in FIG. 3A, the brad rivet 300 includes a head340 and a tail 360, each including a set of deformable legs. A first leg362 and a second leg 364 are disposed proximate to the tail 360 of thebrad rivet 300, while a third leg 342 and a fourth leg 344 are disposedproximate to the head 340. Like the brad rivets 100, 200 of FIGS. 1, 2A,and 2B, each of the legs 362, 364, 342, 344 includes an interfacefeature configured to engage with the second metal plate 114. Each ofthe first leg 362 and the second leg 364 of the brad rivet 300 includesa tail interface, shown as tail barb 366, while each leg 342, 344 on thehead 340 of the brad rivet 300 includes a head interface, shown as headbarb 346. The brad rivet 300 also includes a pulling member, shown asbreakstem 348 (see FIG. 3A), centered between the third leg 342 and thefourth leg 344. As shown in FIG. 3A, the breakstem 348 extends away fromthe tail 360 of the brad rivet 300 along a longitudinal axis 302 of thebrad rivet 300.

The breakstem 348 is configured to engage with an applicator device tofacilitate installation of the brad rivet 300. A method of installingthe brad rivet 300 includes engaging each of the tail barbs 366 with thesecond metal plate 114 proximate to the outer edge 122 of the secondmetal plate 114. This may be accomplished by first securing a sleeve(not shown) along the length of the brad rivet 300, the sleeveconfigured to compress the each of the legs 362, 364, 342, 344 towardthe longitudinal axis 302 of the brad rivet 300. In an illustrativeembodiment, the sleeve 330 is a hollow cylinder that extends along theentire length of the brad rivet 300 (e.g., the sleeve oriented such thata central axis of the sleeve is substantially parallel to thelongitudinal axis 302). In an illustrative embodiment, the innerdiameter of the sleeve is approximately the same as the first and secondaperture diameters 130, 132. The method includes centering the centralaxis of the sleeve 330 with respect to a central axis of the firstaperture 118 and ejecting the brad rivet 300 from the sleeve 330directly into the first and second aperture 118, 120.

The method further includes pulling back on the breakstem 348 (e.g.,away from the tail 360 of the brad rivet 300 in a directionperpendicular to an outer surface 124 of the first metal plate 112),which compresses the first leg 362 and the second leg 364 togethertoward the longitudinal axis 302 of the brad rivet 300. The brad rivet300 elongates as a separation distance 368 between the first leg 362 andthe second leg 364 decreases. This process continues until each of thethird leg 342 and the fourth leg 344 engage with the first metal plate112 proximate to an edge of the first metal plate 112, shown as upperedge 136. The method concludes by separating the breakstem 348 from thebrad rivet 300, by bending, twisting, or upon application of apredetermined force by the applicator device.

In the illustrative embodiment shown in FIG. 4, the head interface foreach leg 442, 444 of the brad rivet 400 includes a plurality ofbarb-like features. As shown in FIG. 4, the head interface furtherincludes a second head barb 450 disposed just below head barb 446 on thetail facing side of the head barb 446. Similar to head barb 446, thesecond head barb 450 is a small projection that extends away from eitherthe third leg 442 or fourth leg 444 in a direction that is substantiallyperpendicular to one of the third leg 442 and the fourth leg 444. Usingmultiple head barbs 446, 450 permits the brad rivet 400 to be tightenedby discrete amounts during installation. Among the various benefits,multiple head barbs 446, 450 allow a single brad rivet 400 design toaccommodate workpieces of varying thickness. Using multiple head barbs446, 450 also provides a mechanism for adjustment of the tensile forcesthat secure the workpieces together.

In various illustrative embodiments, the method of installation of thebrad rivet 300, 400 may be different. For example, transferring the bradrivet 300, 400 from the sleeve into one of the first and secondapertures 118, 120 may be greatly simplified in an embodiment where auser is provided access to both sides of the stack 110 of joinedworkpieces. Furthermore, the length and geometry of the sleeve may bealtered depending on the material properties and geometry of the bradrivet 300, 400.

A variety of geometries are contemplated for the head interface. In oneembodiment, the head interface takes the form of a saw tooth patternalong a surface of each of the third leg and fourth leg. In anotherembodiment, the head interface is formed in the shape of a hook oranother geometry that is configured to latch or engage with the firstmetal plate 112.

An additional illustrative embodiment of a brad rivet 500 is generallydepicted in FIG. 5. Again, the brad rivet 500 includes a head portion,shown as head 540 and a tail portion, shown as tail 560, which isdisposed on an opposite end of the brad rivet 500 as the head 540. Asshown in FIG. 5, the head 540 and tail 560 are separate components thatengage with one another via a threaded interface 572. Like the bradrivets 100, 200 of FIGS. 1, 2A and 2B, the head 540 of the brad rivet500 is formed in a domed shape having a planar lower surface, shown atflat lower surface 542. During installation, the flat lower surface 542is brought into contact with the outer surface 124 of the first metalplate 112. The threaded interface 572 includes a threaded extension 574disposed centrally on the flat lower surface 542 of the head 540. Thethreaded extension 574 is received within a threaded hole 576 on thetail 560.

In the embodiment of FIG. 5, the tail 560 and head 540 of the brad rivet500 are both made from BMG, although the head is not configured todeform elastically. Alternatively, the head may be made from anothermaterial (e.g., a steel alloy, etc.). Again, the tail 560 includes afirst leg 562 and a second leg 564 that are configured to elasticallydeform or deploy on an opposite end of the stack 110 of workpieces onceinserted into the aperture 116. As shown in FIG. 5, the tail 560 extendsthrough the second aperture 120 and a portion of the first aperture 118.In other embodiments, the tail 560 extends through only a portion of thefirst aperture 118.

Advantageously, the tensile forces generated by the brad rivet 500 ofFIG. 5 may be easily adjusted via the threaded interface 572 afterinstallation. In an illustrative embodiment, the head 540 may include afastener interface configured to engage with a fastening tool. In oneembodiment, the fastener interface is one of a variety of types of screwdrive (e.g., hex, slot drive, etc.). In another embodiment, the head 540is a hex head cap screw or another type of bolt.

An illustrative embodiment of a bucked-type rivet assembly, shown asrivet assembly 600, is provided in FIG. 6. The rivet assembly 600includes a formable member, shown as rivet piece 602 and an anvil, shownas forming piece 604. The forming piece 604 is configured to be receivedwithin a channel 606 of the rivet piece 602. The rivet piece 602 isshown isolated from the forming piece 604 in FIG. 7A, while the formingpiece 604 is shown isolated from the rivet piece 602 in FIG. 7B.

As shown in FIG. 7A, the rivet piece 602 includes a head portion, shownas head 608, disposed on a first end of a shaft, shown as cylindricalextension 610. In an illustrative embodiment, the rivet piece 602 isformed as a single piece from an amorphous metal alloy. As with the bradrivets shown in FIGS. 1, 2A-2B, and 5, the head 608 of the rivet piece602 is formed in a domed shape having a planar lower surface, shown atflat lower surface 612, that is configured to contact one of the firstmetal plate 112 and the second metal plate 114 (also see FIGS. 9-10).The cylindrical extension 610 of the rivet piece 602 has an outerdiameter that is sized to fit within both the first aperture 118 and thesecond aperture 120 simultaneously.

A variety of suitable amorphous metal alloys may be used for the rivetpiece 602. Amorphous metal alloys having a reasonably largethermoplastic processing window or supercooled liquid region areparticularly appealing for this application. The subcooled liquid region(ΔTx) is defined as a separation (e.g., temperature difference) betweena temperature (Tx) associated with the onset of crystallization and theglass transition temperature (Tg). Suitable amorphous metal alloys mayinclude a BMG alloy having a subcooled liquid region ΔTx=Tx−Tg within arange between about 20° C. and 130° C. or greater. Other possiblecandidates include titanium, iron, and nickel-based BMG alloys. Yetother possible candidates include zirconium-based BMG, which may bealloyed with one, or a combination of, copper, nickel, titanium,aluminum, and beryllium. The zirconium BMG may also be alloyed with oneor more group three elements as minor alloying additions such as Yttriumand Scandium to improve the viability of commercial-scale production.

In the embodiment of FIGS. 6 and 7B, the forming piece 604 is configuredto be at least partially disposed in an opening, shown as channel 606,that extends along a central axis of the rivet piece 602. As shown inFIG. 7B, the forming piece 604 includes an interface shaft, shown aspuller shaft 616 having a first end and a second end. The forming piece604 also includes an anvil head, shown as forming head 618, disposed ona first end of the puller shaft 616. A portion of the puller shaft 616is configured to separate from the forming piece 604 upon application ofa predetermined tensile force to the puller shaft 616. A separationpoint, shown as notch 620, is disposed at an axial position along thelength of the puller shaft 616 proximate to the forming head 618. Thenotch 620 is configured to weaken the puller shaft 616 so that it breaksupon application of a predetermined force. The notch 620 may be any oneof a variety of different geometries; for example, the notch 620 may bea v-shaped channel, a u-shaped channel, a rectangular channel, or anycombination thereof. In the illustrative embodiment of FIGS. 6 and 7B,the notch 620 is a v-shaped channel that extends around the perimeter ofthe puller shaft 616.

The forming head 618 is configured to plastically deform the tail 660 ofthe rivet piece 602. In an illustrative embodiment, the forming piece604 is made from an electrically conductive material having a largercross-sectional area than the rivet piece 602 along the path of currentflow to reduce Joule heating within the forming piece 604. The formingpiece 604 may also be made from a material with a higher melting pointthan the BMG to prevent the forming piece 604 from plastically deformingwith the tail 660 and/or before the tail 660.

A variety of different materials may be used for the forming piece 604,including steels and hard copper beryllium alloys, both of which haveelectrical conductivities that are higher than BMG. Suitable steelalloys may have electrical conductivities of approximately 10% of theInternational Annealed Copper Standard (IACS) or greater, whereassuitable copper beryllium alloys may have electrical conductivitieswithin a range between 15-45% IACS or greater. Both of these alloyfamilies also have relatively high thermal conductivity, which isnecessary in order to quench the BMG back down below the glasstransition temperature (Tg) before devitrification can occur. Anotherexample of a suitable materials for the forming piece 604 are aluminumalloys. Among other benefits, aluminum alloys tend to be less expensive,have lower hardness, but higher electrical and thermal conductivitiesfor more efficient and faster heating and cooling operations. Althoughaluminum alloys are not as hard as copper or steel alloys, above Tg theBMG alloys significantly soften and become viscous, so although wearingand deformation of the anvil will occur over time, the aluminum basedforming piece 604 could potentially be a more economical solution insome implementations. More complex designs for the forming piece 604 arealso feasible to deliver the electrical current more efficiently to theBMG. For example, a very high electrical conductivity pathway (such as awire) could be incorporated into a pocket and/or opening disposed in theforming piece to deliver the electrical current directly to the surfaceof the rivet instead of requiring the current to travel through theforming piece 604 for heating. The high conductivity pathway may beinsulated from the forming piece 604. Alternatively, the forming piece604 may be configured such that a portion of the current flows throughthe forming piece 604, while simultaneously a portion of the currentflows through the high electrical conductivity pathway.

The forming head 618 of FIGS. 6 and 7B is formed in a U-shape whenviewed in cross-section, whose ends curve back toward the puller shaft616. In other embodiments, the forming head 618 may be formed in aT-shape when viewed in cross-section (see FIGS. 9-10), or another shapethat suitably forms the rivet piece 602 around the outer edge 122 of thesecond aperture 120. As shown in FIG. 6, a second end of the pullershaft 616, opposite the forming head 618, is configured to be receivedwithin the channel 606. As shown in FIG. 6, the second end of the pullershaft 616 extends beyond the head 608 of the rivet piece 602 along acentral axis of the rivet piece 602 and is configured to be receivedwithin an applicator device, shown as rivet tool 622 (see FIG. 8).

A flow diagram of a method 900 of installing a rivet assembly is shownin FIG. 9, according to an illustrative embodiment. The rivet assemblymay be the same or similar to the rivet assembly 600 described withreference to FIGS. 6-8. For simplicity, similar numbering will be usedto identify similar components. The method 900 is illustratedconceptually in FIGS. 10 and 11. The method 900 includes inserting thecylindrical extension 610 of the rivet piece 602 through the firstaperture 118 and the second aperture 120, at 902, such that the flatlower surface 612 of the head 608 contacts an outer surface 124 of thefirst metal plate 112. The method 900 further includes inserting theforming piece 604 into the channel 606 of the rivet piece 602 from anopposite side of the stack 110 (e.g., from the second metal plate 114toward the first metal plate 112), at 904, such that the forming head618 is brought into contact with the cylindrical extension 610.

A variety of techniques may be used to deform the rivet piece 602 usingthe forming piece 604. For example, the rivet piece 602 may be heated toa forming temperature based on the size and material composition of therivet piece 602 and then deformed using the forming piece 604. In orderto heat the rivet piece 602, the rivet tool 622 (see FIG. 8) mayincorporate resistive heaters or another suitable heating device.Alternatively, the rivet tool 622 may be configured to rapidly excitethe forming piece 604 while it is in contact with the rivet piece 602.For example, the rivet tool 622 may be configured to excite the formingpiece 604 using ultrasonic energy. Alternatively, the rivet tool 622 maybe configured to rapidly spin the forming piece 604 to generate heat atthe interface between the forming piece 604 and the rivet piece 602.

In the illustrative embodiment of FIGS. 9-11, the rivet piece 602 isheated, at 906, by passing current through an electrical circuit thatincludes the puller shaft 616, the forming head 618, and the rivet piece602, arranged in series. The electrical circuit is completed by therivet tool 622 (see FIG. 8), which is in contact with both the pullershaft 616 and the head 608 of the rivet piece 602. As shown in FIGS.10-11, the puller shaft 616 is separated from the rivet piece 602 by anannular gap 624 and an insulating layer, shown as layer 626, that isdisposed on a surface of the forming piece, shown as cylindrical outersurface 628. The layer 626 prevents the electrical circuit from shortingacross the annular gap between the forming piece 604 and the rivet piece602 during the heating stage.

In the method 900 of FIG. 9, the rivet tool 622 (see FIG. 8) isconfigured to pull on the second end of the forming piece 604 whilesimultaneously passing a current through the electrical circuit, at 908.Among other benefits, the method of using an electrical current to heatthe rivet piece 602 is fast, controllable, and heats the rivet piece 602directly rather than indirectly. Once heated, the rivet piece 602 beginsto thermoplastically deform proximate to the interface between the rivetpiece 602 and the forming head 618, compressing together each of themetal plates 112, 114. The method 900 further includes breaking theinterface shaft, at 910. As shown in FIG. 11, the notch 620 in thepuller shaft 616 is dimensioned so that at a known load the forming head618 separates from the puller shaft 616. The forming piece 604 is thenremoved from the rivet assembly 600, leaving behind the rivet piece 602.In the embodiment of FIGS. 10-11, the current is switched off to allowthe rivet piece 602 to cool to a hardened fully amorphous state prior toor during separation of the forming head 618 from the puller shaft 616.

A gas or liquid delivery system (not shown) may be coupled to the rivettool 622 to help quench the rivet piece 602 after the heating stage.Among other benefits, a rapid quench prevents devitrification of the BMGduring the cooling stage. The rivet tool 622 may be configured toprovide and circulate a stream of gas (e.g., nitrogen, an inert gas,etc.) or liquid (e.g., water) through the annular gap 624 between theforming piece 604 and the rivet piece 602. The rivet tool 622 may beconfigured to administer the gas or liquid beginning at approximatelythe same time as the current is switched off or just before the currentis switched off to shorten the overall duration of the installationprocess.

In an illustrative embodiment, the rivet piece 602 may be configured tothermoplastically deform on both sides of the stack 110 to achieve verylow profiles of the rivet piece 602 on either side of the stack 110. Forexample, in an illustrative embodiment the rivet piece 602 is a shaft(e.g., a solid shaft of approximately the same geometry as the aperture116) that is deformed by placing a forming head against the rivet piece602 on either side of the stack 110 (e.g., placing a first forming headof a first forming piece against the rivet piece 602 proximate to thesecond metal plate 114, and placing a second forming head of a secondforming piece against the rivet piece 602 proximate to the first metalplate 112). Among other benefits, forming the rivet piece 602 from bothsides creates a joint with as little gap as possible (e.g., a hermeticseal) between the rivet piece 602 and both the metal plates 112, 114.Furthermore, unlike traditional steel rivets whose microstructure isaltered during the forming process, the heated BMG may be readily formedinto a variety of shapes without altering the material properties (e.g.,strength, etc.) of the BMG.

A bucked-type rivet made from BMG may be formed in one of a variety ofdifferent shapes and sizes. In an illustrative embodiment (not shown),at least one of the first and second aperture 118, 120 have an irregularshape in cross-section (e.g., square, oval, T-shape, cross, or a largeropening of any shape). The bucked-type rivet may also be irregularlyshaped to accommodate the geometry of the resulting aperture 116 beforeforming, resulting in improved contact force mechanics between thebucked-type rivet and the workpieces being joined (e.g., the metalplates 112, 114). Alternatively, the bucked-type rivet may take the formof two separate rivet plates. The rivet plates are placed on oppositesides of the stack 110. Heat and pressure are applied to each rivetplate from either side of the stack 110 to form the rivet platestogether through any openings between the workpieces. Such aconfiguration is particularly beneficial when a hermetic seal is desiredalong the joint.

As utilized herein, the terms “approximately,” “about,” “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the disclosure as recited inthe appended claims.

The term “coupled,” as used herein, means the joining of two membersdirectly or indirectly to one another. Such joining may be stationary(e.g., permanent or fixed) or moveable (e.g., removable or releasable).Such joining may be achieved with the two members coupled directly toeach other, with the two members coupled to each other with a separateintervening member and any additional intermediate members coupled withone another, or with the two members coupled to each other with anintervening member that is integrally formed as a single unitary bodywith one of the two members. Such members may be coupled mechanically,electrically, and/or fluidly.

The term “or,” as used herein, is used in its inclusive sense (and notin its exclusive sense) so that when used to connect a list of elements,the term “or” means one, some, or all of the elements in the list.Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is understood to convey that anelement may be either X, Y, Z; X and Y; X and Z; Y and Z; or X, Y, and Z(i.e., any combination of X, Y, and Z). Thus, such conjunctive languageis not generally intended to imply that certain embodiments require atleast one of X, at least one of Y, and at least one of Z to each bepresent, unless otherwise indicated.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” etc.) are merely used to describe the orientation ofvarious elements in the FIGURES. It should be noted that the orientationof various elements may differ according to other exemplary embodiments,and that such variations are intended to be encompassed by the presentdisclosure.

Although the figures and description may illustrate a specific order ofmethod steps, the order of such steps may differ from what is depictedand described, unless specified differently above. Also, two or moresteps may be performed concurrently or with partial concurrence, unlessspecified differently above. Such variation may depend, for example, onthe software and hardware systems chosen and on designer choice. Allsuch variations are within the scope of the disclosure. Likewise,software implementations of the described methods could be accomplishedwith standard programming techniques with rule-based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps, and decision steps.

What is claimed is:
 1. A blind rivet made at least partially from anamorphous metal alloy, the blind rivet comprising: a head portion; atail portion comprising a first leg and a second leg, wherein an end ofeach of the first leg and the second leg comprises a tail interface; anda pulling member disposed on the head portion of the blind rivet,wherein the pulling member extends away from the tail portion of theblind rivet along a longitudinal axis of the blind rivet, wherein: thehead portion of the blind rivet is configured to engage with a firstmember, the tail interface for each of the first leg and the second legis configured to engage with a second member, at least one of the firstleg and the second leg is configured to elastically deform to secure thefirst member in position relative to the second member, and the pullingmember is configured to generate a tensile force on the blind rivet andsimultaneously a compressive force that acts to reduce separationbetween the first leg and the second leg when the tail portion isengaged with the second member.
 2. The blind rivet of claim 1, whereinthe amorphous metal alloy comprises a bulk metallic glass (BMG) alloy.3. The blind rivet of claim 2, where the BMG alloy has an elastic limitof about 2% strain or greater.
 4. The blind rivet of claim 1, whereinthe blind rivet is configured to be secured in position relative to thesecond member by the compressive force.
 5. The blind rivet of claim 1,wherein the head portion is configured to deform elastically whensecuring the first member to the second member.
 6. The blind rivet ofclaim 1, further comprising a sleeve disposed on the tail portion,wherein the sleeve exerts a second compressive force on the first legand the second leg that prevents the first leg and the second leg fromseparating.
 7. The blind rivet of claim 6, wherein the sleeve isconfigured to be positioned within an aperture in the first member. 8.The blind rivet of claim 1, wherein the head portion further comprises ashaft, and wherein the head portion and the tail portion are separable.9. The blind rivet of claim 8, wherein the shaft is threaded into thetail portion.
 10. The blind rivet of claim 1, wherein the head portioncomprises: a third leg; a fourth leg, wherein the pulling member isdisposed proximate to the third leg and the fourth leg, wherein each ofthe third leg and the fourth leg comprises a head interface, wherein thehead interface is configured to engage with the first member, wherein atleast a portion of the pulling member is configured to be removed fromthe blind rivet during installation of the blind rivet.
 11. The blindrivet of claim 10, wherein the head interface comprises a plurality ofbarb-like features, and wherein each one of the plurality of barb-likefeatures is configured to engage with the first member.
 12. The blindrivet of claim 11, wherein the plurality of barb-like features arespaced along a length of a respective one of the third leg and thefourth leg.
 13. The blind rivet of claim 1, wherein the tail interfacecomprises a barb, and wherein the barb is configured to engage with thesecond member.
 14. The blind rivet of claim 1, wherein the first leg andthe second leg are in a shape formed by splitting a shaft along a planeextending through a longitudinal axis of the shaft.